Hi,
the answer to the question is quite evident, to answer you, as you know an error is being generated each time you add a style. Of course this is not what you are realy asking for. If you close PPress and reststart the software does the issue go away ?
Also depending on your answer can you reproduce this at will ?
We will most probably need your v.c.d. for troubleshooting purposes, to do so you must report an issue by pressing report an issue button top left corner of this page.
Let me know how it goes.
Thanks